The present invention relates to phenolic binder formulations. More particularly, the present invention pertains to a urea modified phenol-formaldehyde composition containing melamine, melamine derivatives, and/or ammonium lignosulfonate (hereinafter also referred to as xe2x80x9cligninxe2x80x9d). The binder compositions of the present invention produce lower gaseous emissions, while at the same time add to the overall stability of the premix and binder system. The binders of the present invention are particularly useful in the manufacture of glass wool insulation materials.
Phenol-formaldehyde binders have been widely used in the manufacture of glass fiber and glass wool insulation materials. They have a low viscosity in their uncured state, yet form a rigid thermoset polymeric matrix for the glass fibers when cured. A low binder viscosity in the uncured state allows for the vertical expansion of the coated mat when it exits the forming chamber, while the rigid matrix of the cured product ensures that the finished fibrous glass thermal or acoustical insulation product returns to its original dimensions after it has been compressed for packaging and shipping.
However, the phenol-formaldehyde resole binders contain a fairly large excess of formaldehyde from the manufacturing process. For environmental reasons and in order to lower the amount of phenol used in the manufacture of these phenolic binders, a much higher ratio of formaldehyde to phenol is used in the preparation of the resole part of the phenol-formaldehyde binder. Therefore, more recently, the phenol-formaldehyde resole binders have been modified using urea. Urea is added to the phenol-formaldehyde resole to react with the free formaldehyde. Upon completion of this process for manufacturing the urea modified phenol-formaldehyde binder the free formaldehyde level is well below 1% of the amount of formaldehyde used. However, due to the vast amounts of binder used in the manufacture of insulation products, the release of that free formaldehyde into the environment is a concern. Further, it has been found that the modification of these phenol-formaldehyde resole resins with urea reduces the stability of the resin. Accordingly, there is a need for improved urea modified phenol-formaldehyde binder formulations with greater stability, and which emit lower gaseous materials into the environment. In particular, there is a need for binders which emit lower levels of phenol, formaldehyde and ammonia.
The use of urea and ammonia as formaldehyde scavengers for use in phenol-formaldehyde resins is disclosed in U.S. Pat. No. 3,956,205. Further, U.S. Reissue Pat. No. 30,375 discloses the use of ammonia to raise the pH of a binder including a resole resin, urea and an acid catalyst for elevated temperature cure of the binder. U.S. Pat. No. 4,757,108 discloses a phenolic resole-urea composition made by the reaction of urea with the free formaldehyde in the phenolic resole resin under acid conditions, the composition subsequently being made neutral or slightly basic by further addition of urea. The aforementioned U.S. patents are herein incorporated by reference.
This invention relates to compositions that allow for reduced emissions from phenolic binders. Further, the present invention also relates to phenolic binder compositions having improved binder stability and accelerated cure rates.
The phenolic binders of the present invention comprise:
(a) a premix of a urea modified phenol-formaldehyde resole resin;
(b) a curing agent; and
(c) an additive selected from the group consisting of at least one of ammonium lignosulfonate, melamine, and melamine derivative.
Further objects, features and advantages of the present invention will become apparent from the detailed description that follows.